DC voltage multiplication has been implemented by various types of DC-to-DC converters. The classic approach to such multiplication involves the use of an oscillator for converting the DC voltage to an alternating one, which is then stepped-up by a transformer and rectified to produce the higher DC level. An alternate method of multiplication in common use utilizes an oscillator and a diode-capacitor voltage multiplier. Each of these methods has deficiencies. The transformer type is adapted to higher power levels but tends to be bulky, costly and inefficient at light loads. The capacitive type, which may be designed for efficiency at light loads, has inherently poor regulation and limited power-handling capability. In general the well known voltage multiplier requires a plurality of capacitors and diodes, each equal in number to the degree of multiplication. For example, a voltage doubler requires two capacitors and two diodes, a tripler, three of each component. When considering higher levels of multiplication, such as an octupler, the component count becomes prohibitively large.
The availability of low-resistance CMOS voltage-controlled solid state switches and of low power digital circuits, including microprocessors, makes possible the mechanization of more compact capacitive type multipliers. At the same time, the low operating voltages of such digital circuits, typically of the order of five volts, creates a need for voltage multiplication when significant output energy is needed for interfacing with certain utilization devices. For example, electroexplosive devices are commonly initiated by discharge of a capacitor through a bridge wire surrounded by a heat-sensitive compound. It is desirable that the energy be delivered as rapidly as possible to minimize heat loss, that is, the RC time constant of the wire and storage capacitor should be as small as possible. This condition dictates the use of a small capacitor charged to a relatively high voltage. Furthermore, with relation to the capacitive storage of energy, any increase in voltage results in a much more sizeable decrease in the value of the required capacitance. Since the capacitor provides a reservoir of energy deliverable at a high rate, the voltage multiplier can operate at a very low current rate, that is, a rate sufficient to supply capacitor leakage current.
The present invention provides circuit means for charging a storage capacitor and maintaining the charge thereon, in a highly efficient manner and with a minimal component count. For example, in the octupler, chosen for purposes of disclosure hereinafter, the theoretical eight-fold multiplication of the supply voltage is achieved with four capacitors and four diodes, including the output storage capacitor. It should be understood however, that the basic techniques described herein are directly applicable to other levels of multiplication.